Chemical sequencing and control to expand and enhance detection capabilities utilizing a colorimetric test

ABSTRACT

Embodiments of the present disclosure pertain to a colorimetric system for detecting a substance, the colorimetric system that includes a first chemical container adapted for releasing a first chemical; a second chemical container adapted for releasing a second chemical; a flow modulation sheet adjacent each chemical container; and an encapsulation covering the flow modulation sheet and each chemical container, where the encapsulation comprises a window defining a target area of the filter paper such that the target area is adapted for applying the substance; where the flow modulation sheet comprises a design adapted for automatically controlling a first flow of the first chemical and a second flow of the second chemical to the target area after simultaneously releasing the first and second chemicals; and where the design comprises a first void disposed in the flow modulation sheet.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Pat. No. 11,179,718, issuedon Nov. 23, 2021, which is a continuation of U.S. Pat. No. 10,500,584,issued on Dec. 10, 2019, which is a continuation of U.S. Pat. No.9,724,689, issued on Aug. 8, 2017, which is a national stage applicationof PCT/US2013/032603 that claims priority to U.S. Provisional PatentApplication No. 61/728,519 filed on Nov. 20, 2012. The entirety of eachof the aforementioned patents and applications are incorporated hereinby reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not applicable.

BACKGROUND

Colorimetric testing is utilized in many industries to determine thepresence or degree of presence, e.g. concentration in solution, ofparticular substances. For example, chlorine test kits have been used todetermine the general concentration of chlorine level in swimming pools.In another example, early pregnancy tests detect the presence of acertain hormone in female during pregnancy. Both of these examplesillustrate the use of a colorimetric test to determine the presence ordegree of presence of a substance. In these examples, the color changeis visible to the human eye and is typically observed directly by aperson conducting the test.

United States Patent Application Publication US20090325300 describes acard component for use in conjunction with a spectral detection unituseful for detecting trace materials including biohazards, toxins,radioactive materials, narcotics, and explosives. In particular,US20090325300 discloses, at paragraph [0043], that a sample of anunknown trace material is collected on a card component. Reaction of theunknown trace materials sample collected on the on the pad is initiatedwith liquid reagents and dissolved compounds contained in at least oneflexible walled capsule embedded in the card component, wherein thereaction is initiated after inserting the card in the chemical detectionunit causing walls of the capsules to yield to fluid flow, establishingfluid communication between the capsules and the pad. This isaccomplished by releasing chemicals and other contents of the firstcapsule and applying heat to stimulate reaction with the unknown tracematerial. The fluid communication may be established via specific pathslike grooves or similar structural means, or using wicks. Further,chemicals from the capsules may be released in a fashion to react inspatially distinct regions of the pad or the regions may be temporallyseparated for chemical reactions. The spectral pattern is observed andrecorded by the chemical detection unit. With respect to release ofchemicals from capsules to react in spatially distinct regions of thereaction pad, US20090325300, at paragraph [0047] discloses that that inan embodiment the reaction pad can be divided into three separate fluidchannels each in proximity to a specific capsule. In this way threeseparate color reactions can be produced spatially in a side-by-sideconfiguration rather than in timed sequence. With respect to release ofchemicals from capsules to temporally separated regions of the reactionpad, US20090325300, at paragraph [0049], discloses that in one preferredembodiment the first of two capsules capsule is activated and anysequence of color changes is recorded. The second capsule is thenactivated and the color recorded.

In some colorimetric tests a prior chemical reaction modifies thecharacteristics of the substance under test in order to be able toexecute a subsequent test that requires molecular modification prior totesting for a particular substance. A well-known example is theapplication of the Griess reaction as the second stage of a two stagereaction scheme to detection of nitroglycerin. The reaction schemeinvolves two solutions. In the first stage, the reaction scheme involvesadding a preliminary alkaline solution containing a base tonitroglycerin to produce nitrite ions. In the second stage, the reactionscheme involves adding an acidic solution Griess reagent mixture to thenitrite ions to produce a colored product. An exemplary base is sodiumhydroxide. An exemplary acid Griess reagent mixture includessulphanilamide and 2-naphthylamine in a phosphoric acid solution. TheGriess reaction involves reaction of sulphanilic acid with the nitritesto produce diazonium ions, coupled with reaction of the dizonium ionsreact with 2-naphthylamine to produce a colored Griess reaction product,both occurring in the same Griess solution. It is desirable to timeadding the preliminary alkaline solution containing a base prior toadding the acidic Griess solution containing the Griess reagent mixturebecause the reaction conditions of the first stage are alkaline and thereaction conditions of the Griess reaction are acidic, thereforediffering in pH. Combining the alkaline and acidic solutions would tendto neutralize the pH, thus negatively affecting the test.

Notwithstanding the above teachings, there remains a need forcolorimetric test systems and methods that provide for accurate timingcontrol and sequencing of different chemicals. More particularly, thereremains a need for colorimetric systems and methods for controlling thearrival of chemicals to a reaction pad in a colorimetric card that donot require temporally separate release of the chemicals.

SUMMARY

In some embodiments, the present invention provides a colorimetricsystem and method for controlling the arrivals of chemicals to a targetarea after simultaneous release from respective chemical containers. Thesystem and method may involve two or more pairs of chemical and chemicalcontainer. Thus, the system and method may involve at least two pairs ofchemical and chemical container. The system and method may involve aflow modulation sheet designed so as to control the flows of thechemicals. The flow modulation sheet may contain the target area. Thesystem and method have the advantage of providing for accurate relativetiming of the arrivals of the chemicals to the target area.

In some embodiments, the present disclosure pertains to a colorimetricsystem for detecting a substance, the colorimetric system that includesa first chemical container adapted for releasing a first chemical; asecond chemical container adapted for releasing a second chemical; aflow modulation sheet adjacent each chemical container; and anencapsulation covering the flow modulation sheet and each chemicalcontainer, where the encapsulation comprises a window defining a targetarea of the filter paper such that the target area is adapted forapplying the substance; where the flow modulation sheet comprises adesign adapted for automatically controlling a first flow of the firstchemical and a second flow of the second chemical to the target areaafter simultaneously releasing the first and second chemicals; and wherethe design comprises a first void disposed in the flow modulation sheet.In some embodiments the present disclosure pertains to a colorimetricmethod comprising providing the colorimetric system for detecting asubstance; applying the substance to the target area; and simultaneouslyreleasing the first and second chemicals.

Controlling the first and second flows may include controlling a firsttiming of the first flow and a second timing of the second flow.Controlling the first and second timings may include regulating a firstspeed of the first flow and a second speed of the second flow.Alternatively or in combination, controlling the first and secondtimings of the first and second flows comprises may include controllinga first arrival of the first chemical to the target area and a secondarrival of the second chemical to the target area. The first arrival maybe earlier than second arrival. The arrival a respective chemical may bethe arrival of a leading edge of the flow of the respective chemical toan edge of the target area. The arrival of a respective chemical may bethe arrival of at least 80% of the respective chemical to the full areaof the target area. Controlling the first and second flows may includereducing dripping of the first and second chemicals. Reducing drippingof the first and second chemicals may include substantially preventingdripping of the first and second chemicals.

The colorimetric system and method may be adapted for upright use of thecolorimetric system. The design of the flow modulation sheet mayaccommodate flows of the first and second chemicals under the influenceof gravity.

The design of the flow modulation sheet may include a thickness of thevoid. The encapsulation may be made by controlling bonding of a firstencapsulation piece and a second encapsulation piece so as to controlthe thickness.

The design of the flow modulation sheet may include a shape of the firstvoid. The shape may include a width and a length. The width may be lessthan the length. The size of the first void may be adapted to theviscosity of the first chemical, or a solution containing the firstchemical in solution. For example, length may be increased withincreasing viscosity.

The design of the flow modulation sheet may include a layout of thefirst void. The first void may be between the first chemical containerand the target area. Further, the first void may be adjacent the firstchemical container.

The design of the flow modulation sheet may include a second voiddisposed in the flow modulation sheet. The design of the flow modulationsheet may include a first shape of the first void and a second shape ofthe second void. The first shape may include a first length, the secondshape may include a second length. The second length may be less thanthe first length. The difference in lengths may be adapted to delay thearrival of the second chemical to the target area relative to thearrival of the first chemical.

The design of the flow modulation sheet may include a layout of thefirst void and a layout of the second void. The second void may bebetween the second chemical container and the target area. A portion ofthe flow modulation sheet may be between the second void and the secondchemical container. Alternatively, the second void may be adjacent thesecond chemical container.

The design of the flow modulation sheet may include a notch near thetarget area, where the notch is along a path of the second flow. Thenotch may be adapted for reducing dripping of the second chemical.

The flow modulation sheet may be made of a porous sheet of fibers. Theporous sheet of fibers may be made of a porous paper. The first chemicalcontainers may be made of a first ampoule. The first ampoule may be aglass ampoule. The second ampoule may be a second ampoule. The secondampoule may be a glass ampoule. The encapsulation may be made ofplastic. The plastic may include polyvinyl chloride.

The first and second chemicals may be chemicals associated with thefirst stage and second stages respectively of a multiple stagecolorimetric reaction scheme. The first chemical may be in a firstsolution. The second chemical may be in a second solution. It is withinthe skill of one of ordinary skill in the art to select a known multiplestage colorimetric reaction scheme. The first chemical may modify amolecular structure of the substance so as to produce an intermediate.The first chemical may break down the substance so as to produce anintermediate. The second chemical may be reactive with the intermediateso as to produce a color. The color may be detectable with the humaneye. Alternative, or in combination, the color may be detectable with adetection device. For example, the color may be detectable with thespectral detection unit described in US20090325300.

The colorimetric system may be a colorimetric card. The colorimetriccard may be suitable to use with the spectral detection unit. Afterinserting the colorimetric card into the spectral detection unit, thespectral detection unit may be used to initiate release of thechemicals. When the release is initiated manually, by pushing on asingle portion of the spectral detection unit, the present colorimetricsystem and card and the advantage of that simultaneous release of thechemicals may be consistently repeated because both releases areinitiated with the same push. Thus, the colorimetric system and methodhave the advantage of providing for accurate and consistent colorimetrictesting.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a side view of an embodiment of the present colorimetricsystem;

FIG. 2 shows an exploded view of the embodiment shown in FIG. 1;

FIG. 3 shows a side view of an alternative embodiment of the presentcolorimetric system;

FIG. 4 shows a side view of another alternative embodiment of thepresent colorimetric system;

FIG. 5 shows a side view of yet another alternative embodiment of thepresent colorimetric system;

FIG. 6 shows a side view of still another alternative embodiment of thepresent colorimetric system;

FIG. 7 shows a side view of an embodiment of a filter paper beforeassembly and trimming;

FIG. 8 shows a side view of an alternative embodiment of a filter paperbefore assembly and trimming; and

FIG. 9 shows a side view of another alternative embodiment of a filterpaper before assembly and trimming.

DETAILED DESCRIPTION

It is to be understood that both the foregoing general description andthe following detailed description are illustrative and explanatory, andare not restrictive of the subject matter, as claimed. In thisapplication, the use of the singular includes the plural, the word “a”or “an” means “at least one”, and the use of “or” means “and/or”, unlessspecifically stated otherwise. Furthermore, the use of the term“including”, as well as other forms, such as “includes” and “included”,is not limiting. Thus, for example, “includes” encompasses “includes,but is not limited to”. Also, terms such as “element” or “component”encompass both elements or components comprising one unit and elementsor components that comprise more than one unit unless specificallystated otherwise.

It is to be understood that “filter paper” is used herein to denote aporous nonwoven sheet of vegetable fibers. It is to be understood thatas used herein “paper” denotes a felted, also termed nonwoven, sheet offibers, where the fibers are vegetable fibers. Further, as used herein“filter paper” denotes porous paper. It is to be understood that theuses herein of “paper” and “filter paper” are consistent with the commonmeanings of “paper” and “filter paper”. Exemplary vegetable fibers knownto one of ordinary skill in the art are wood fibers, cotton fibers, andthe like. It is within the skill of ordinary skill in the art to selecta suitable nonwoven porous sheet of vegetable fibers. For example,wood-based filter paper and cotton-based nonwoven buckram paper are eacha suitable porous paper for the present system and method.

It is to be understood that “channel” as used herein denotes a regionsuitable for flow. It is to understood that as used herein “air channel”denotes a channel provided as a void. It is to be understood that, whenin use, an air channel may receive a flow of a chemical there through.

The elements used in the present disclosure provide timing control andsequencing of different chemicals with much greater accuracy. Thepresent disclosure, details how expanded and enhanced tests can beperformed, which significantly expand the test capabilities of thecolorimetric approach and how they can be used in real worldapplications. Controlling the flow of chemical in automated colorimetricsystems tends to involve controlled release of the chemical (gating), aswell as control of the chemical as to when it reaches the target areafor the colorimetric reaction post gating. Gating of the chemical is theprimary determining factor that establishes the gross timing. However,precise control of the timing for the chemical to reach the targetedarea, can provide enhanced colorimetric testing that could not beachieved with other methods. Precise control of the chemical flow aftergating can be achieved by utilizing various methods to control theoverall timing. This is especially desirable when timed sequentialgating is not an option.

In some embodiments, the present disclosure pertains to mechanisms tosequence and control the flow of chemicals in defined environments. Insome embodiments, the chemical is stored in a chemical container. Insome embodiments, a glass ampoule would be an example of a chemicalcontainer. Thereafter, the chemical can be released from the chemicalcontainer in a controlled fashion. In some embodiments, a timingcomponent may be present, where chemicals can be released together. Itwill be understood that “released together” denotes releasedsimultaneously.

The present approach allows for the sequencing of chemicals so thatcertain substances can be detected that require multiple reactions to bedetected. Sequencing is the process of controlling the arrival of achemical to a targeted “test area” in an automated fashion so thatmultiple individual chemical reactions can take place. This is desirablein some colorimetric tests where a prior chemical reaction modifies thecharacteristics of the substance under test in order to be able toexecute a subsequent test that requires molecular modification prior totesting for a particular substance.

In various embodiments, chemical flow from a chemical container to atest area can be controlled by implementation of a filter papermechanism, with suitable material characteristics, coupled with designstructures of the paper layout that influence chemical flow. The filterpaper modulates flow characteristics of chemicals therein. Thereforefilter paper is illustrative herein of a flow modulation sheet.

Design structures of the filter paper include design of an air channel,which has a first order effect on the chemical flow. Thickness of thecard and compression of the filter paper can also be uniquely specifiedto control chemical flow. In some embodiments, this can be accomplishedby control of the bonding mechanism used to encapsulate the filterpaper.

In various embodiments, the elements used in the present disclosureinclude, without limitation, implementing an “air” channel in a filterpaper, tighter control of the RF welding process in order to controlthickness of the air channel, and modifying the shape characteristics ofthe channel to modify chemical flow behavior. Examples of thesevariations are illustrated in FIGS. 1-9 and described herein.

Referring now to FIG. 1, colorimetric system 100 includes encapsulation110, filter paper 120, first chemical container 130, second chemicalcontainer 140, window 150, first air channel 160, second air channel170, notch 180, and main channel 190. First chemical 135 is contained infirst container 130. Second chemical 145 is contained in secondcontainer 140. Main channel 190 is U-shaped and has two subchannels, onefor each combination of chemical container and air channel. Filter paper120 includes discontinuous portions 122 outside of alignment with mainchannel 190 and continuous portion 124 aligned with main channel 190.Notch 180 is in filter paper 120. Notchmate 185 is in encapsulation 110.Notchmate 185 aligns with notch 180. Filter paper 120 includes first airchannel 160 therethrough and second air channel 170 therethrough. Filterpaper 120 includes test area 126. Test area 126 is defined by window150. Encapsulate 110 includes window 150 therethrough. Encapsulate 110includes first cavity 197 therein and second cavity 199 therein. Firstcontainer 130 rests in first cavity 197. Second container 140 rests insecond cavity 199. Air vent channel 195 is connected to main channel190. Encapsulation 110 includes hole 155 therethrough. Hole 155 isaligned so as to provide an opening to air vent channel 195.

Referring now to FIG. 2, an exploded view of colorimetric system 100 isshown. First encapsulate piece 114 and second encapsulate piece 112 arebonded to form encapsulate 110.

In some embodiments, physical characteristics of the air channel can beused to regulate the speed of fluid flow in the test card. In someembodiments, the length, width and shape of the air channel can beadjusted to influence the fluids dynamics of the flow.

Referring now to FIGS. 3-6, various alternative second air channels 370,470, 570, and 670 are shown. The variations illustrate variations inlayout and length of an air channel.

Referring now to FIG. 7, first air channel 760 and registration holes725 are shown in a filter paper before assembly and trimming. Referringto FIGS. 8-9, various alternative first air channels 860, and 960 areshown and an alternative second air channel 970 is shown.

Welding specifications of the plastic encapsulation also affectschemical flow and is controlled based upon the materials and filterpaper design used. Design considerations for the card are reflected inthe method of making the card. The welding, also termed bonding herein,involves use of aluminum tools for radiofrequency (RF) heating of theplastic encapsulation. Some design considerations follow.

Installing an air vent channel may include modifying a thermoform moldtool to put an indentation in the air vent channel. Installing an airvent channel may further include, during cut and trim operation,inserting a hole using the indentation as a locator. This maintains theconsistency of the location and size of the air vent hole. The air venthole may be punched in the encapsulation after welding.

Making the card edges smooth may include making a top RF tool and abottom RF tool oversized. Making the card edges smooth may furtherinclude cutting the card from the resulting oversized welded parts. Thismoves the edge of the RF weld out. Therefore when cut in the cuttingtool, the edge will be smooth. Before welding, oversize componentshaving registration holes may be aligned using the registration holes.Referring to FIG. 7, registration holes 725 are illustrated. Both filterpaper and first and second encapsulation pieces may be oversized beforealigning, welding, and cutting.

Modifying the main channel so liquid enters at more contact points tothe path may include adjusting the width of the main channel. Adjustingthe width of the main channel may include adjusting the RF insulator.Adjusting the width of the main channel may include adjusting athermoform mold. Adjusting the thermoform mold permits adding channelsto direct flow to saturate the pad, also termed herein the test area,also termed herein the target area, from the back side as well as theedges.

A Rayform channel support may be used. It is desirable to mill theRayform insert to fit exactly with the main channel part of the mold.

It will be understood that the above description reveals that thepresent colorimetric system may be made by providing a bottom RF mold,an RF insulation, and a Rayform insert; placing a back encapsulationprecursor having registration holes over the bottom RF mold, insertingfirst and second chemical containers; inserting a filter paper precursorhaving registration holes; adding a front encapsulation precursor havingregistration holes; topping with a top RF mold; aligning the precursors;applying RF heat so as to bond the back and front encapsulation pieces;and trimming the precursors.

Embodiments of the present disclosure can be used to detect substancesthat require more than one chemical reaction to perform a colorimetricreaction. Embodiments include having to use a chemical reaction tomodify the molecular structure of a substance before a second definedchemical reaction can be executed to provide for the colorimetricreaction process to identify the substance in the colorimetric reaction.An example of this embodiment is if a particular molecule needs to becleaved off by a prior reaction, before the colorimetric test will work.By controlling the chemical flow and having chemical #1 react, prior tohaving chemical #2 being introduced to the subject test area, sequentialchemical reactions can be produced in a control fashion that otherwisewould not be possible. In various embodiments, timing of chemical flowis an important component to repeatable and reliable reactions.

By way of example and not limitation, the present colorimetric systemand device are suitable for controlling the conventional two stagecolorimetric Griess-based reaction scheme to test for nitroglycerin.

The methods and apparatus of the present disclosure have significantflexibility in design and implementation. Therefore, the methods andapparatus of the present disclosure are adaptable to many differenttypes of conditions.

Furthermore, in various embodiments, additional types of chemicals canbe added to provide more complex molecule manipulation and thereforedetection, which cannot be achieved with other means.

In some embodiments, chemical flow characteristics can be adjusted andmodified based on manipulating chemical viscosity through adjustment ofwater to solvent ratios. There are many ways by which to use thechemical viscosities to adjust flow. More than two chemicals can beadded to the card, which would involve further chemical flow parameters.

Furthermore, chemical flow may sometimes be impeded by a highconcentration of acid used in the detection chemical makeup. Therefore,in various embodiments, different techniques of stimulating the flow ofacids can be employed by changing channel design and layout. In variousembodiments, ventilation and doping materials may also be used to affectchemical flow. Additional methods may also be used to adjust the filterpaper and channel makeup in the chemical flow process that can be vettedand utilized.

Further refinement and control of the chemical flow can also bepossible. Such refinements can lead to increased repeatability in thetesting, as well faster test results. This can provide additionaladvantages of the historical method of manually sequencing this type oftest as the total test time can be reduced, which can dramaticallyimprove utilization of this process in the marketplace.

The implementation of automated control of this chemical sequencingeliminates manual intervention and provides much higher reliability andquality of control where sequential chemical reactions are required.

An advantage of utilizing the methods and apparatus of the presentdisclosure is that they greatly expand the capabilities of acolorimetric test. With control of chemical flow as described,Applicants can make a device that can test many substances thatpreviously could not be tested in a controlled and/or automated fashion.By controlling the flow of chemicals in a quantitative, repeatablefashion, dramatically improved repeatability and quality of the chemicalprocess is achievable.

Without further elaboration, it is believed that one skilled in the artcan, using the description herein, utilize the present disclosure to itsfullest extent. The section headings used herein are for organizationalpurposes and are not to be construed as limiting the subject matterdescribed. The embodiments described herein are to be construed asillustrative and not as constraining the remainder of the disclosure inany way whatsoever. While the embodiments have been shown and described,many variations and modifications thereof can be made by one skilled inthe art without departing from the spirit and teachings of theinvention. Accordingly, the scope of protection is not limited by thedescription set out above, but is only limited by the claims, includingall equivalents of the subject matter of the claims. The disclosures ofall patents, patent applications and publications cited herein arehereby incorporated herein by reference, to the extent that they provideprocedural or other details consistent with and supplementary to thoseset forth herein.

What is claimed is:
 1. A system for detecting a substance, the systemcomprising: a first container adapted for releasing a first chemical; asecond container adapted for releasing a second chemical; and a flowmodulation material comprising: a target area-adapted for applying thesubstance a first portion comprising a first channel disposed betweenthe first container and the target area, and a second portion comprisinga second channel disposed between the second container and the targetarea, wherein the flow modulation material is adapted for controlling afirst flow of the first chemical and a second flow of the secondchemical to the target area after releasing the first and secondchemicals.
 2. The system for detecting a substance according to claim 1,further comprising an encapsulation covering the flow modulationmaterial and each container, wherein the encapsulation comprises awindow defining the target area.
 3. The system for detecting a substanceaccording to claim 2, wherein the encapsulation comprises a plastic. 4.The system for detecting a substance according to claim 1, wherein thefirst channel and the second channel have different lengths.
 5. Thesystem for detecting a substance according to claim 4, wherein thedifferent lengths contribute to different chemical flow characteristics.6. The system for detecting a substance according to claim 1, whereinthe flow modulation material is in the form of a porous sheet.
 7. Thesystem for detecting a substance according to claim 7, wherein theporous sheet comprises a porous paper.
 8. The system for detecting asubstance according to claim 1, wherein the first container comprises afirst glass ampoule and the second container comprises a second glassampoule.
 9. The system for detecting a substance according to claim 1,where the first channel and the second channel have different chemicalflow characteristics.
 10. The system for detecting a substance accordingto claim 9, wherein the different chemical flow characteristics comprisedifferent speeds of fluid flow.
 11. The system for detecting a substanceaccording to claim 1, wherein the first channel comprises a void withinthe first portion of the flow modulation material.
 12. The system fordetecting a substance according to claim 1, wherein the second channelcomprises a void within the second portion of the flow modulationmaterial.
 13. The system for detecting a substance according to claim 1,wherein the first portion is near the first container.
 14. The systemfor detecting a substance according to claim 1, wherein the secondportion is near the second container.
 15. A method for detecting asubstance, comprising: applying the substance to a target area of asystem, wherein the system comprises: a first container adapted forreleasing a first chemical, a second container adapted for releasing asecond chemical, and a flow modulation material comprising: the targetarea, a first portion comprising a first channel disposed between thefirst container and the target area, and a second portion comprising asecond channel disposed between the second container and the targetarea, wherein the flow modulation material is adapted for controlling afirst flow of the first chemical and a second flow of the secondchemical to the target area after releasing the first and secondchemicals; and releasing the first and second chemicals.
 16. The methodof claim 15, wherein controlling the first flow and the second flowcomprises controlling a first timing of the first flow and a secondtiming of the second flow by regulating a first speed of the first flowand a second speed of the second flow.
 17. The method of claim 15,wherein controlling the first flow and the second flow comprisescontrolling a first timing of the first flow and a second timing of thesecond flow by controlling a first arrival of the first chemical to thetarget area and a second arrival of the second chemical to the targetarea.
 18. The method of claim 17, wherein the first flow of the firstchemical arrives at the target area earlier than the second flow of thesecond chemical.
 19. The method of claim 17, wherein the first portionis near the first container and the second portion is near the secondcontainer.
 20. The method of claim 15, wherein the releasing comprisessimultaneously releasing the first and second chemicals.